In an orthogonal frequency division multiple access (OFDMA) transmission manner used in the wireless local access network (WLAN for short) standard 802.11ax, a time length of an orthogonal frequency division multiplexing (OFDM) symbol that does not include a cyclic prefix (CP) is 12.8 μs. In a frequency domain, a smallest resource unit (RU) includes 26 subcarriers. Typically, 24 subcarriers are used to carry useful information and are referred to as data subcarriers, and two pilot subcarriers are used to correct a phase deviation caused by a frequency offset and phase noise. To reduce channel contention, an access point (AP) always tries to transmit as much data as possible in one transmission opportunity. For example, if duration of one transmission opportunity is 5.1 ms, 100 μs are used to transmit a preamble of a physical-layer packet, and CP duration is 0.8 μs, a data field part may include about (5.1 ms-100 μs)/(12.8 μs+0.8 μs)=368 OFDM symbols. It is assumed that a modulation and coding scheme (MCS) MCS 4 corresponding to a medium signal-to-noise ratio (SNR) is used, that is, 16 quadrature amplitude modulation (QAM) and convolutional coding whose code rate is 3/4 are used. One RU is used to transmit about 368×4×3/4×24/8=3312 bytes.
However, in actual application, there are a large quantity of applications of small data packet transmission, for example, interactive media, online gaming, user operation and control in office cloud application, instant messaging, web browsing, and the like. Generally, even if all data in one station is transmitted by using one RU, to meet a requirement for timely data transmission, the station cannot fully use, in a limited time period, the RU occupied by the station. Therefore, the RU needs to be padded with a useless bit, and low resource utilization is caused.